The List-Unsubscribe header is a component of email headers, used by marketers and email administrators to provide an easy opt-out mechanism for recipients.
The primary purpose of the List-Unsubscribe header is to combat spam and enhance the user's control over their inbox. Essentially, it provides a method for the recipient to send an unsubscribe request to the sender's email domain directly from their email client, instead of having to manually click on an unsubscribe link, login to a website, or take other additional steps.
How can this be activated in Odoo?